A power conversion device generates and supplies three-phase AC voltages to a load by combining ON/OFF states of switching elements that constitute a PWM three-phase inverter. In this power conversion device, respective-phase currents that flow through a three-phase load such as a motor are detected, and the load is controlled on the basis of the detected respective-phase currents.
As a unit that detects the respective-phase currents that flow through the three-phase load, a current sensor or a shunt resistance is provided, which is connected in series to the switching elements that constitute the inverter. As a configuration including a shunt resistance, a power-supply shunt resistance is provided that detects a current between a DC power supply and an inverter device or a lower-arm shunt resistance that detects a phase current of the corresponding phase is provided between a lower-arm switching element and the negative side of the DC power supply. With the configuration including the power-supply shunt resistance or the lower-arm shunt resistance, it is necessary to specify a detected phase current in each phase. This complicates the control software. Further, with the configuration including the power-supply shunt resistance, when a current for a single phase can only be detected, it is necessary to adjust the energization in order to detect currents for two phases. That is, in one switching cycle, the period for detecting each phase current is limited to a narrow range. Therefore, an inverter device is disclosed that can detect a phase current using simple control software that does not need to specify a detected current in each phase, to adjust energization, or to detect a current in a time-series manner, for example, by means of “providing a power-supply shunt resistance and lower-arm shunt resistances for at least two phases and detecting, by using the power-supply shunt resistance, a phase current that cannot be detected by the lower-arm shunt resistances” (for example, Patent Literature 1).